Liquid coolant in a cooling system, such as for an engine, can become aerated. Aeration of liquid coolant can lead to cavitation of an engine coolant pump, engine erosion due to air in the system, pitting of engine liners, engine overheating, cab HVAC system failures, EGR cooler erosion, and other drawbacks.
Pressurized coolant surge tanks, which pressurize the cooling system to raise the boiling point of the liquid coolant, have been used in cooling systems to de-aerate liquid coolant. A regulatory orifice allows a portion of the liquid coolant to pass through the surge tank for de-aeration. The surge tank has a cap with a pressure-relief valve that allows air under pressure in the surge tank to vent to atmosphere. Compared to non-pressurized coolant overflow tanks, surge tanks are relatively expensive and occupy a fair amount of space on board a vehicle.